Leaders from Istanbul, Madrid and Tokyo were handing over their documents at the headquarters of the International Olympic Committee [IOC] on Monday, setting the stage for the final eight months of a global campaign featuring three cities bidding again after previous defeats.

Madrid is bidding for a third consecutive time, Tokyo a second time in a row and Istanbul a fifth time overall.

The so-called "bid books" run to several hundred pages and represent the cities' master plan of venues, budgets, financial guarantees, security, accommodations, transportation and other key aspects of the multi-billion-dollar projects.

The files are to be released publicly by the bid cities on Tuesday.

The IOC's evaluation commission, headed by Craig Reedie of Britain, will visit the cities in March and prepare a report for IOC members before a meeting with the bidders in Lausanne in July.

The full IOC will select the host city in a secret ballot in Buenos Aires on September 7.

'Tokyo as the favourite'
The 2020 field initially included six candidates, but Rome dropped out when the Italian government refused to offer financial support and the IOC cut Doha, Qatar and Baku, Azerbaijan from the list last year.

Istanbul is bidding again after failed attempts for the Olympics of 2000, 2004, 2008 and 2012. Madrid is back after finishing third for the 2012 Olympic Games and second for 2016.
Tokyo, which hosted the 1964 Olympics, finished third in the voting for 2016.

Tokyo received the highest praise in an IOC technical report last year which said the Japanese bid presents "a very strong application". Madrid has a "strong application", while Istanbul's project "offers good potential", the report said.

While bookmakers list Tokyo as the favourite, Istanbul holds the advantage of representing a new destination for the Olympics – a key factor in recent host city votes.

The IOC is taking the 2014 Winter Games to the Russian city of Sochi, the 2016 Olympics to Rio de Janeiro and the 2018 Winter Games to Pyeongchang, South Korea.

Geopolitical and economic challenges
All three bids for 2020 face geopolitical and economic challenges.

Spain is in the throes of its second recession in just over three years, with its economy battered by a collapse in the real estate sector and unemployment as high as 25%.

Madrid bid leaders said the Olympics could serve as a catalyst for economic recovery.

Japanese leaders have said hosting the Olympics in Tokyo would serve a symbol of recovery from the disastrous earthquake and tsunami in 2011.

Japan has also been in a nasty dispute with China over a cluster of disputed islands in the East China Sea and has just undergone a change in government that brought Shinzo Abe to power as prime minister.

Istanbul, meanwhile, is seeking the Olympics at a time when Turkey is in conflict with Syria. Turkey is a former ally of Syria but turned against President Bashar Assad's regime over its violent crackdown on dissent in the nearly two-year civil war that has left 60 000 dead.

Turkey is supporting the Syrian opposition and rebels and is providing shelter to some 150 000 refugees. – Sapa-AP